This section provides background information related to the present disclosure which is not necessarily prior art.
Typically, automotive vehicles including cars and trucks have an internal combustion engine (gasoline or diesel) which is coupled to at least a transmission and a differential for providing power to the driven wheels of the vehicle. An engine exhaust system which typically includes one or more exhaust pipes, one or more turbochargers, one or more catalytic converters, one or more mufflers and one or more tailpipes is attached to the engine to quiet the combustion process, to clean the exhaust gases and to route the products of combustion away from the engine. The internal combustion engine is supported in the vehicle on a set of flexible engine mounts which are positioned between a frame or other supporting structure and the engine. The exhaust system is supported by exhaust mounts which are positioned between the exhaust system and the frame or other supporting structure of the vehicle's body. In order to minimize engine vibrations from being transmitted to the vehicle's body, the exhaust mounts incorporate flexible mounting members and/or elastic suspension members.
Even with using the flexible engine mounts and the flexible exhaust mounts, the operation of the engine at the various operating conditions for the engine can cause offensive noise, vibration or harshness (NVH) issues. Various solutions to these NVH issues have been proposed. A frequency NVH issue can be addressed by adding dead mass weights to the system, adding a tuned damper and/or adding a coulomb damper.
The addition of dead mass weights to the system will simply shift the natural frequency of the system to a lower frequency. Adding a tuned damper will only address a specific frequency. The tuned damper accomplishes this by shifting the natural frequency amplitude into a lesser amplitude at a frequency above and below the original. A coulomb damper is comprised of a canister filled with impact media such as shot or sand. A coulomb damper is a broadband solution which is sensitive to the quantity, density, geometry and friction of the impact media inside the canister. In addition, the efficiency of the energy transmission from the exhaust system into the impact media of the coulomb damper is critical to the operation and effectiveness of the coulomb damper.